Incorrectly selected or installed downlighters can the cause of fires in homes

(26/02/2010)

The Electrical Safety Council (ESC) have been working with the Surrey Fire and Rescue Service to investigate concerns that incorrectly selected, installed and/or maintained downlighters may have been the cause of a significant number of fires in homes.

As part of the investigation, they commissioned an independent laboratory to carry out a limited safety assessment of, and thermal performance testing on, a selection of commercially-available downlighters. Eight downlighters were selected to include a broad range of lamp type, fitting design and price, and assessed against the requirements for safety and performance specified in product standards applicable to ‘recessed luminaires’.

In essence, the downlighters were first tested when installed in accordance with the manufacturers’ instructions, and then when covered over with two layers of 100 mm thick thermal insulation.

For all but one of the downlighters, covering the luminaire was considered to be an ‘abnormal’ mode of operation which contravened the installation instructions. However, being covered in thermal insulation or other material is reportedly one of the main reasons for downlighters being the source of fires.

Summary of the findings

All of the downlighters failed to meet one or more of the tests and inspections performed during the assessment.

Seven samples failed to provide appropriate markings, warnings and/or user instructions. Of particular concern was the number of instances where important safety information marked on fittings (such as the rated wattage, ingress protection rating and suitability for mounting on combustible surfaces) was found to conflict with details given on product packaging and in the installation instructions. In one case, two labels had been attached to the fitting, each indicating a different rated wattage!

Also, labels had been attached to the exterior surface of fittings and would therefore be hidden once installed and when lamps were being replaced.

Endurance testing was performed by operating the downlighters for a period of 10 days mounted in a purpose-built enclosure, taking into account the installation instructions.

After the test, to comply with the standard, the downlighters should not show any signs of deterioration or have caused damage to their surroundings. Four of the samples failed this endurance test. Subsequent inspection revealed discoloration of internal painted surfaces due to heat from lamps, and discoloration and peeling of labels making them unreadable. In two instances, overheating had caused scorching of wood surfaces around the fitting.

Thermal testing was performed by operating the downlighters at their rated ambient temperature and when fitted with a lamp type specified by the manufacturer.

The most widely available type of tungsten halogen lamp on the high street is the ‘cool beam’ or dichroic reflector lamp. A dichroic lamp has a reflector made of a material that reflects visible light forwards while allowing radiated heat to pass out of the back of the lamp, resulting in a beam of light that is ‘cooler’. The alternative type of lamp is made with an aluminium reflector that reflects both light and heat forwards and out of the front of the lamp.

As the bases of the most common types of push-fit extra-low voltage dichroic and aluminium reflector lamps are identical, it is possible to fit either type in any extra-low voltage downlighter.

However, most extra-low voltage downlighters are not designed to operate safely with both types of lamp. For example, aluminium reflector lamps are generally specified for downlighters having integral fire protection to ensure that heat radiated by the lamp is not directed back into the fire containment compartment of the luminaire.

The interchangeability issue is a concern because, while preparing for the laboratory tests, we found it difficult to find the aluminium reflector type lamp in any of the normal retail sources over quite a wide area, or indeed in wholesalers. Therefore, even if consumers were aware of the need to select the correct lamp type for their particular downlighters, they might purchase the wrong type as a matter of necessity or expediency.

Where appropriate, additional thermal testing was performed on downlighters with incorrect lamps types fitted to simulate an abnormal (but foreseeable) mode of operation.

During the tests, no part of the downlighters should exceed the limiting temperatures specified in the product standard.

Three of the samples failed the thermal test with specified lamps fitted, and a further two samples failed the abnormal thermal test with incorrect lamps fitted.

In three cases, the temperature of the test recess mounting hole exceeded the specification limit of 90 oC. The highest recorded temperature was 115 oC. In two cases, the insulated wiring at the lampholder exceeded the specified limit of 200 oC, the highest measured temperature being 219 oC. A recorded temperature of 171 oC immediately above one downlighter was almost twice the limit of 90 oC specified in the relevant product standard.

Many other instances of temperatures exceeding specified limits were noted, both for the luminaires and associated parts such as transformer cases and supply cables, but were within the allowable tolerances and so not recorded as failures.

In addition to the four samples that failed the initial thermal endurance test, a further sample failed the additional endurance test when covered with thermal insulation.

Under these conditions, one of these five downlighters failed to operate for the required duration of ten days. An inspection after test revealed that the lampholder wiring had burnt out. For another sample, heavy scorching was observed around the recess through which the downlighter was mounted.

In a further case, significant scorching of the test recess above the downlighter was observed. During the test period, it was noted that the lamp failed, the most likely cause being excessive temperature rise.

Conclusions

It would appear evident from the findings that the design of, the markings and instructions provided with, and the thermal performance of downlighters are significant factors that can increase the risk of fire where the minimum requirements of relevant product standards are not met.

Following further discussions with the Surrey Fire & Rescue Service and the Department for Communities and Local Government (CLG), it is felt that enough evidence has been amassed from the laboratory testing and anecdotal evidence to support a UK-wide awareness campaign to deliver key safety messages about the potential fire risks of downlighters.

As with all product safety investigations undertaken, they are following up all the identified failures with the retailers and manufacturers concerned, and keeping the relevant authorities informed of their actions.

Anyone who has reason to believe they have purchased an unsafe downlighter should contact their local authority trading standards office in the first instance.

Related categories:  Lamps   Residential